Where in the world to go with an infant in September?

[mollymore]

Hey folks, it's been a few months, or years, LOL

I'm having a baby in June. Yay! And I'm planning to take a trip in September. That's about as far as I've gotten. I need help!

First thing's first: Where to go?! Where is there good weather in september? Budget is a serious consideration. Where are places that will be easier navigate and find cheap accommodations with an infant?

A little more information:
We're 2 adults and a 2-3 month old infant. I would like to go somewhere off the continent (departing from Vancouver or Seattle) for 2-3 weeks including travel time. The cheaper it is, the longer we can stay! I'm thinking it would be nice to stay in 2 different spots at our destination, one more rural, one more urban, and make one or two overnight stops as we travel between these places.

Suggestions please!